An open top hopper or gondola-type railway car typically comprises a series of side walls, end walls and vertical posts that define the basic perimeter of a container for handling a body of material. The posts are spaced along the side walls and are designed to strengthen and reinforce the side walls of the container. A top chord structure extends along each of the side walls of the container to further strengthen and stablize the side walls.
In the handling of material, it is often necessary to subject the top chord of an open top hopper or gondola-type railway car to some high localized forces. For example, in unloading the contents of the car into a rotary dumper, it is conventional to clamp the top chord as the car is tilted or turned into an unloading position. Also, it is conventional to apply a shaker to the top chord of the car to agitate the contents of the car during the unloading process. Both such operations impose large localized forces on the top chord.
A top chord construction that has been used in the past has a P-shaped profile. That is, the chord has a tubular member with a generally rectangular profile, and a stem that is integrally connected with the tubular member. The stem is designed to be bolted to the side wall and the post of the container, in the manner illustrated in FIG. 5, in order to connect the chord to the container. More specifically, the side wall is a relatively flat, planar member, and the post is a generally U-shaped member with a pair of co-planar flanges that are juxtaposed with the side wall, with the legs of the U-shaped post extending outward from the side wall. The stem of the P-shaped top chord is then bolted to the side wall and to the post flanges in order to connect the top chord with the container. As shown in FIG. 5, the stem is bolted to the post with the side wall disposed between the stem and the post.
With the P-shaped chord profile shown in FIG. 5, the tubular, rectangular chord section of the chord is normally disposed above the post and the side wall. Also, the stem is spaced from the post. The forces applied to the top chord produce a high bending moment on the chord stem, and that bending moment can stress the chord and its fasteners to an undesirable extent, especially in the joint area where the stem of the chord is bolted to the post.
A particular problem with the chord structure of FIG. 5 is slippage in the area of the fastener. Specifically, when the chord of FIG. 5 is subjected to a high bending moment, the stresses on the fastener tend to cause cocking of the stem in the area of the fastener. With the stem spaced from the post, and the side wall sandwiched therebetween, the joint structure allows such cocking of the stem, and under high bending moments, such cocking can result in slippage in the joint area.
Another type of known top chord construction has a relatively flat chord section (rather than a tubular chord section), an integral stem for attachment to the side wall, and a lip connected with the chord section and designed to rest upon the side post. An additional reinforcing plate is bolted to the side wall and the stem of the top chord, with the side wall sandwiched between the stem and the reinforcing plate. The additional reinforcing plate functions to strengthen the joint between the side wall and the stem, to minimize the effect of bending moments applied to the top chord. However, that construction requires the additional reinforcement plate, and the chord itself is less stable than a tubular section. Additionally, it is not believed to be as effective as the structure of the present invention for minimizing the problem of slippage in the area of the fastener.